From: Ales Marecek <amarecek@...>
Date: 2011-09-13T23:17:01+09:00
Subject: [ruby-core:39521] [Ruby 1.9 - Bug #4576] Range#step miss the last value, if end-exclusive and has float number


Issue #4576 has been updated by Ales Marecek.


Hi!
Shyouhei, I can't agree with you. We have some fact that algorithm written in ruby doesn't work. I know this is not the problem of ruby but it is fixable. If we have something like tests there, we run it, what it is for when it fails? If there is no reason to fix bug like this what is the reason for fixing anything? Then, we could drop all tests and pretend everything works well. I think it should NOT work like this.
As Vit said, changing value in test case is absolutely nonsense, it's good for nothing, it's not a fix! Leave this alone is bad too because we have some algorithm that doesn't work - why use it then? Why have it in code?

Michal, do you think that this kind of information is correct ---> [1.0, 2.9, 4.8, 6.699999999999999]? I do NOT. What's wrong there, try to guess. Yes, you have three numbers with one decimal and the last one with many, that's not correct! That's not correct in Math view and same in Physics. Correct could be [1.0, 2.9, 4.8, 6.6] or [1.0, 2.9, 4.8, 6.7] OR [1.000000..., ....] (depends on round method.
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Bug #4576: Range#step miss the last value, if end-exclusive and has float number
http://redmine.ruby-lang.org/issues/4576

Author: Joey Zhou
Status: Closed
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: -


=begin
Hi, I find that:

* if: range.exclude_end? == true
* and: any one in [begin_obj, end_obj, step] is a true Float(f.to_i != f)
* and: unless begin_obj + step*int == end_obj
* then: the result will miss the last value.

for example:

 p (1...6.3).step.to_a # => [1.0, 2.0, 3.0, 4.0, 5.0], no 6.0
 p (1.1...6).step.to_a # => [1.1, 2.1, 3.1, 4.1], no 5.1
 p (1...6).step(1.1).to_a # => [1.0, 2.1, 3.2, 4.300000000000001], no 5.4

 p (1.0...6.6).step(1.9).to_a # => [1.0, 2.9], no 4.8
 p (1.0...6.7).step(1.9).to_a # => [1.0, 2.9, 4.8]
 p (1.0...6.8).step(1.9).to_a # => [1.0, 2.9, 4.8], no 6.7

Maybe the #step is ok on integers, but there's something wrong if the range is end-exclusive and contain float numbers.
=end



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